US6445684B1 - Method and system for dynamic adjustment of CDMA wireless device power levels - Google Patents
Method and system for dynamic adjustment of CDMA wireless device power levels Download PDFInfo
- Publication number
- US6445684B1 US6445684B1 US09/203,305 US20330598A US6445684B1 US 6445684 B1 US6445684 B1 US 6445684B1 US 20330598 A US20330598 A US 20330598A US 6445684 B1 US6445684 B1 US 6445684B1
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- Prior art keywords
- movement
- rate
- wireless device
- wireless devices
- base station
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- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
- H04W52/04—TPC
- H04W52/18—TPC being performed according to specific parameters
- H04W52/28—TPC being performed according to specific parameters using user profile, e.g. mobile speed, priority or network state, e.g. standby, idle or non transmission
- H04W52/282—TPC being performed according to specific parameters using user profile, e.g. mobile speed, priority or network state, e.g. standby, idle or non transmission taking into account the speed of the mobile
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
- H04W52/04—TPC
- H04W52/18—TPC being performed according to specific parameters
- H04W52/28—TPC being performed according to specific parameters using user profile, e.g. mobile speed, priority or network state, e.g. standby, idle or non transmission
- H04W52/285—TPC being performed according to specific parameters using user profile, e.g. mobile speed, priority or network state, e.g. standby, idle or non transmission taking into account the mobility of the user
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
- H04B1/707—Spread spectrum techniques using direct sequence modulation
Definitions
- the present invention relates generally to code division multiple access (CDMA) communication systems and, more particularly, to power control for CDMA communication systems.
- CDMA code division multiple access
- CDMA Code division multiple access
- PCS personal communication service
- CDMA Code division multiple access
- a digital signal located at a wireless device is multiplied at the wireless device by a unique code corresponding to that device, which spreads the digital signal over a greater bandwidth. For example, a 10 kHz signal may be multiplied by a code which effectively creates a 100 kHz spread signal.
- the spread signal modulates a carrier frequency signal which is in the range of the uplink frequency channel.
- the modulated carrier is then transmitted from the wireless device to the base station.
- the base station receives a composite spread signal of all the modulated carrier frequency signals from all wireless devices transmitting at that point in time.
- the base station demodulates the composite spread signal and then partially despreads the demodulated signal using the same unique code used at a particular wireless device for spreading.
- the despread signal approximates the pre-spreading data signal for the particular wireless device.
- a fixed user is a user that stays in place or moves at a relatively low rate of speed such as when walking during a call.
- a mobile user is a user that moves at a relatively high rate of speed such as when traveling in a vehicle during a call. All users are located within a sector of the base station for wireless communication with the base station.
- each user in the sector is allocated the same amount of power to communicate with the base station.
- the measure of power allocated to each user is defined as the ratio of energy per bit to the noise power spectral density (Eb/No).
- the Eb/No level for each user is measured at the base station.
- the Eb/No level is set at the same level for all users in the sector and is dictated by the needs of mobile users. Unfortunately, this leads to a waste of resources for fixed users whose Eb/No level may be lower.
- Eb/No decibels
- Eb/No correlates to greater capacity.
- Eb/No level i.e., approximately three decibels less
- optimal base station capacity can be maintained while maintaining the quality of service for both fixed and mobile users. Consequently, what is needed is a method and system which dynamically adjusts Eb/No levels as a function of the needs of the users.
- the present invention provides a method for controlling transmitted power of wireless devices within a sector of a base station of a code division multiple access (CDMA) communication system.
- the method includes estimating rate of movement of a wireless device.
- the rate of movement of the wireless device is then compared to a given rate of movement threshold interval.
- the transmitted power of the wireless device is then set to a power level corresponding to the given rate of movement threshold interval if the rate of movement of the wireless device falls within the given rate of movement threshold interval.
- the present invention provides another method for controlling transmitted power of wireless devices in a CDMA communication system.
- This method includes estimating rate of movement of each of the wireless devices. An average rate of movement of all of the wireless devices over a given time period is then determined from the estimated rates of movement of each of the wireless devices. The average rate of movement of all of the wireless devices is then compared to a given rate of movement threshold. The transmitted power of all of the wireless devices is then set to a high power level if the average rate of movement of all of the wireless devices is greater than the given rate of movement threshold. Similarly, the transmitted power of all of the wireless devices is set to a low power level if the average rate of movement of all of the wireless devices is less than the given rate of movement threshold.
- the present invention provides yet another method for controlling transmitted power of wireless devices in a CDMA communication system.
- This method includes estimating rate of movement of each of the wireless devices. The rate of movement of each of the wireless devices is then compared to a given rate of movement threshold. The transmitted power of a wireless device is then set to a high power level if the rate of movement of the wireless device is greater than the given rate of movement threshold. Similarly, the transmitted power of a wireless device is set to a low power level if the rate of movement of the wireless device is less than the given rate of movement threshold.
- FIG. 1 is a schematic representation of a personal communication service (PCS) system in accordance with the present invention
- FIG. 2 is a flow diagram representing a specific operation of the method and system of the present invention
- FIG. 3 is a flow diagram representing a specific operation of the method and system of the present invention.
- FIG. 4 is a flow diagram representing general operation of the method and system of the present invention.
- PCS system 10 in accordance with a preferred embodiment of the present invention is shown.
- PCS system 10 includes a base station 12 , a stationary wireless device 14 , a pedestrian wireless device 16 , and a vehicular wireless device 18 .
- Base station 12 transmits and receives code division multiple access (CDMA) wireless data signals with stationary device 14 , pedestrian device 16 , and vehicular device 18 .
- CDMA code division multiple access
- base station 12 and devices 14 , 16 , and 18 include transmitter and receiver modules.
- Stationary wireless device 14 may be a household telephone which remains in place during communication with base station 12 .
- Pedestrian wireless device 16 is a hand-held telephone which moves at a relatively slow rate of speed as the user walks while communicating with base station 12 .
- Vehicular wireless device 18 is a telephone configured for use in a vehicle and moves at a relatively high rate of speed as the user drives the vehicle while communicating with base station 12 via the vehicular wireless device.
- PCS system 10 further includes a mobile switching center 20 and a home location register/visitor location register (HLR/VLR) database 22 operable with mobile switching center 20 .
- Mobile switching center 20 is also connected to a central office 24 via an inter-office trunk 26 .
- Central office 24 is connected to a wireline phone 28 (plain old telephone service (POTS)).
- POTS plain old telephone service
- the Eb/No level of a wireless device is measured at the receiver of base station 12 in conjunction with mobile switching center 20 .
- the reverse link from a wireless device to base station 12 determines the Eb/No level.
- Base station 12 compares the measured Eb/No level with a nominal Eb/No level. If the measured Eb/No level is greater than the nominal Eb/No level, then base station 12 transmits a data message to the wireless device instructing the wireless device to reduce its transmitted power. As the power is reduced, the measured Eb/No level eventually meets the nominal Eb/No level. Similarly, if the measured Eb/No level is less than the nominal Eb/No level, then base station 12 transmits a data message to the wireless device instructing the wireless device to increase its transmitted power.
- the measured Eb/No level eventually meets the nominal Eb/No level.
- the power transmitted by the wireless device is varied to maintain a constant receive power level at base station 12 from all of the wireless devices in use in the sector to minimize cochannel interference and optimize the capacity of the base station.
- the capacity of base station 12 is inversely proportional to the nominal Eb/No level.
- the reverse link closed power control described above minimizes cochannel interference by maintaining a constant Eb/No level.
- Eb/No level With a constant Eb/No level, all wireless devices in the sector transmit at levels where the received power from each wireless device is at the same signal strength as measured by base station 12 . Allocating just enough Eb/No maximizes the capacity of base station 12 while allocating any more power reduces the capacity of the base station.
- Flow diagram 30 representing operation of the system and method according to the present invention is shown.
- the operation described by flow diagram 30 is carried out by base station 12 and mobile switching center 20 .
- Flow diagram 30 differentiates the users in a sector as either being fixed or mobile users.
- the average speed of all of the users in the sector is estimated and then a given Eb/No level is assigned to all of the users as a function of the average speed.
- the given Eb/No level is either a relatively low fixed user Eb/No level if the majority of users are fixed users or is a relatively high mobile user Eb/No level if the majority of users are mobile users.
- block 32 determines the average speed of each user in a sector over a time period (T).
- Block 34 determines the average speed ( ⁇ V T (X)>) of all of the users or a selected percentage or group of users over the time period.
- Block 36 compares ⁇ V T (X)> to a threshold speed v 0 (e.g., 1 m/s). At v 0 , fast fading is not a problem and therefore the required Eb/No level may be lower. If ⁇ V T (X)> is greater than v 0 , the majority of users are mobile users.
- Block 38 sets the Eb/No level for all of the users to the mobile user Eb/No level which is E 1 .
- Block 40 sets the Eb/No level for all of the users to the fixed user Eb/No level which is E 0 . The above process is then repeated with block 32 updating the average speed of each user in the sector.
- each of the fixed and mobile user Eb/No levels include minimum and maximum levels centered around a nominal level.
- the mobile user Eb/No level E 1 includes a nominal Eb/No, a minimum Eb/No, and a maximum Eb/No.
- the minimum Eb/No level ensures capacity and the maximum Eb/No level improves quality.
- the nominal Eb/No level works in conjunction with the set frame error rate (FER) of base station 12 .
- FER frame error rate
- the fading environment becomes less volatile because the mobile user is stationary. Typically, this causes the Eb/No level to be reduced because less mobile transmit power is required to maintain the Eb/No level.
- base station 12 allows the mobile user to keep lowering the mobile transmit power until the minimum Eb/No level is reached. Once the traffic light becomes green and the mobile user goes back into motion, the fading environment becomes more volatile and the mobile user requires more transmit power to maintain a reliable Eb/No level.
- a minimum Eb/No level is required to minimize the time it takes for the Eb/No level measurement process to catch up with the speed of the mobile user. If the mobile user moves too quickly and the minimum Eb/No level is set to low, the base station messaging to increase the mobile power could take too long to reach an acceptable Eb/No level, potentially resulting in degraded service quality and perhaps a dropped call.
- a maximum Eb/No level is required to put an upper limit on the amount of mobile transmit power for situations where overshoot occurs during the catch up process.
- Different processes may be used for determining the average speed of each user over the time period (T) by block 32 .
- These methods include the following. First, a database of profiles for each user having the highest probability of use (fixed or mobile) of the user may be utilized to determine the speed of the user. Second, power control values may be examined. Power control values usually give hints on the amount of fading and therefore provide an estimate of the speed of the users. Third, the variation in time of the path delay information of CDMA parameters for each leg can be used to provide an estimate of the speed of the users. A leg is a term referring to each of the established ice path connections. Fourth, examining the number of different P/N codes used in a past time period.
- Eb/No levels can be examined. If mobile users have an Eb/No level constantly around the minimum mobile user Eb/No level, then these mobile users can be considered as being fixed users. Similarly, if fixed users have an Eb/No level constantly around the maximum fixed user Eb/No level, then these fixed users can be considered as being mobile users.
- GPS global positioning system
- flow diagram 50 representing operation of the system and method according to the present invention is shown.
- the operation described by flow diagram 50 is carried out by base station 12 and mobile switching center 20 .
- flow diagram 50 determines, for each of the users, whether an individual user is fixed or mobile and then assigns a fixed or mobile user Eb/No level to that user.
- Eb/No level the average speed of each of the users is estimated and then a given Eb/No level is assigned to each of the users.
- the given Eb/No level assigned to a user is either a relatively low fixed user Eb/No level is the user is a fixed user or is a relatively high mobile user Eb/No level is the user is a mobile user.
- block 52 determines the average speed v T (X) of each user (x) in a sector over a time period (T).
- Block 54 compares v T (x) to a threshold speed v 0 . If v T (x) is greater than or equal to v 0 , the user is a mobile user.
- Block 56 sets the Eb/No level for the user to the mobile user Eb/No level which is E 1 . If V T (X) is less than v 0 , the user is a fixed user.
- Block 58 sets the Eb/No level for the user to the fixed user Eb/No level which is E 0 . The above process is then repeated with block 52 updating the average speed of each user in the sector.
- Flow diagram 60 representing the general operation of the method and system according to the present invention are shown.
- Flow diagram 60 encompasses three levels of refinement depending upon how many different Eb/No profiles are allowed per sector.
- the first level of refinement is that if only one Eb-No profile is allowed, then a fixed (mobile) user Eb/No level is assigned to all of the users in the sector if the majority of users are fixed (mobile) users. This was described in conjunction with flow diagram 30 of FIG. 2 .
- the second level of refinement is that if two Eb/No profiles are allowed per sector, then, for each user, a fixed (mobile) user Eb/No level is assigned to a user in the sector if the user is a fixed (mobile) user.
- Flow diagram 60 summarizes the level of detail that may be considered (per sector, per class of users, and per individual user).
- block 62 determines the average speed of each user over a time period (T).
- Block 64 then computes the average user speed v T (x) over a time period (T).
- the average user speed v T (x) is either the average speed of all of the users, the average speed of a given class of users, or the average speed of each user.
- Block 66 compares v T (x) to speed thresholds v i and v i ⁇ 1 .
- the speed thresholds determine what Eb/No levels to set. There is only one speed threshold if differentiating between fixed and mobile users. There are two speed thresholds if differentiating between fixed, mobile, and pedestrian users. It should be noted that there may be further reasons to find additional distinctions, e.g., premium users or data/multimedia users that have different Eb/No needs.
- Block 68 sets the Eb/No level to Ei.
- the Ei level is a set of Eb/No settings for a speed threshold interval defined above.
- the Ei level includes minimal Eb/No, maximum Eb/No, and nominal Eb/No.
- the wireless devices have a parameter called the Ec/Io which is analogous to Eb/No at the base station.
- the teachings of the present invention are applicable to adjusting the Ec/Io levels.
- the present invention is applicable to cellular radio systems employing CDMA techniques. Accordingly, the present invention is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims.
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- Computer Networks & Wireless Communication (AREA)
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Abstract
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Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
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US09/203,305 US6445684B1 (en) | 1998-12-01 | 1998-12-01 | Method and system for dynamic adjustment of CDMA wireless device power levels |
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US09/203,305 US6445684B1 (en) | 1998-12-01 | 1998-12-01 | Method and system for dynamic adjustment of CDMA wireless device power levels |
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Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
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US6839781B1 (en) * | 1999-11-22 | 2005-01-04 | Nec Corporation | Wireless keyboard and information processing device having the same |
US20050181817A1 (en) * | 1995-03-31 | 2005-08-18 | Tiedemann Edward G.Jr. | Method and apparatus for performing fast power control in a mobile communication system |
US20060229025A1 (en) * | 2005-03-30 | 2006-10-12 | Lucent Technologies Inc. | Method for extracting optimal reverse link capacity by scaling reverse link Eb/No setpoint based on aggregate channel load and condition |
US7127252B1 (en) * | 1999-04-30 | 2006-10-24 | Fujitsu Limited | Radio terminal equipment |
US7986749B2 (en) | 1995-03-31 | 2011-07-26 | Qualcomm Incorporated | Method and apparatus for performing fast power control in a mobile communication system |
US8199696B2 (en) | 2001-03-29 | 2012-06-12 | Qualcomm Incorporated | Method and apparatus for power control in a wireless communication system |
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US6208873B1 (en) * | 1998-11-23 | 2001-03-27 | Qualcomm Incorporated | Method and apparatus for transmitting reverse link power control signals based on the probability that the power control command is in error |
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1998
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Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
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US20050181817A1 (en) * | 1995-03-31 | 2005-08-18 | Tiedemann Edward G.Jr. | Method and apparatus for performing fast power control in a mobile communication system |
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US7831272B2 (en) * | 1995-03-31 | 2010-11-09 | Qualcomm Incorporated | Method and apparatus for performing fast power control in a mobile communication system |
US7986749B2 (en) | 1995-03-31 | 2011-07-26 | Qualcomm Incorporated | Method and apparatus for performing fast power control in a mobile communication system |
US7127252B1 (en) * | 1999-04-30 | 2006-10-24 | Fujitsu Limited | Radio terminal equipment |
US6839781B1 (en) * | 1999-11-22 | 2005-01-04 | Nec Corporation | Wireless keyboard and information processing device having the same |
US8199696B2 (en) | 2001-03-29 | 2012-06-12 | Qualcomm Incorporated | Method and apparatus for power control in a wireless communication system |
US20060229025A1 (en) * | 2005-03-30 | 2006-10-12 | Lucent Technologies Inc. | Method for extracting optimal reverse link capacity by scaling reverse link Eb/No setpoint based on aggregate channel load and condition |
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